[S390] broken copy_in_user function.

The copy_in_user primitive does not work as advertised. If the source
and target area are available copy_in_user copies one byte too much.
If one of the memory areas is not available it does not copy as much
data as it can, but up to 257 bytes less.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/lib/uaccess.S

@@ -88,30 +88,31 @@ __copy_to_user_asm:
         .globl __copy_in_user_asm
 	# %r2 = from, %r3 = n, %r4 = to
 __copy_in_user_asm:
+	ahi	%r3,-1
+	jo	6f
 	sacf	256
-	bras	1,1f
-	mvc	0(1,%r4),0(%r2)
-0:	mvc	0(256,%r4),0(%r2)
-	la	%r2,256(%r2)
-	la	%r4,256(%r4)
-1:	ahi	%r3,-256
-	jnm	0b
-2:	ex	%r3,0(%r1)
-	sacf	0
-	slr	%r2,%r2
-	br	14
-3:	mvc	0(1,%r4),0(%r2)
+	bras	%r1,4f
+0:	ahi	%r3,257
+1:	mvc	0(1,%r4),0(%r2)
 	la	%r2,1(%r2)
 	la	%r4,1(%r4)
 	ahi	%r3,-1
+	jnz	1b
+2:	lr	%r2,%r3
+	br	%r14
+3:	mvc	0(256,%r4),0(%r2)
+	la	%r2,256(%r2)
+	la	%r4,256(%r4)
+4:	ahi	%r3,-256
 	jnm	3b
-4:	lr	%r2,%r3
+5:	ex	%r3,4(%r1)
 	sacf	0
+6:	slr	%r2,%r2
 	br	%r14
         .section __ex_table,"a"
-	.long	0b,3b
-	.long	2b,3b
-	.long	3b,4b
+	.long	1b,2b
+	.long	3b,0b
+	.long	5b,0b
         .previous
 
         .align 4

arch/s390/lib/uaccess64.S

@@ -88,30 +88,31 @@ __copy_to_user_asm:
         .globl __copy_in_user_asm
 	# %r2 = from, %r3 = n, %r4 = to
 __copy_in_user_asm:
+	aghi	%r3,-1
+	jo	6f
 	sacf	256
-	bras	1,1f
-	mvc	0(1,%r4),0(%r2)
-0:	mvc	0(256,%r4),0(%r2)
-	la	%r2,256(%r2)
-	la	%r4,256(%r4)
-1:	aghi	%r3,-256
-	jnm	0b
-2:	ex	%r3,0(%r1)
-	sacf	0
-	slgr	%r2,%r2
-	br	14
-3:	mvc	0(1,%r4),0(%r2)
+	bras	%r1,4f
+0:	aghi	%r3,257
+1:	mvc	0(1,%r4),0(%r2)
 	la	%r2,1(%r2)
 	la	%r4,1(%r4)
 	aghi	%r3,-1
+	jnz	1b
+2:	lgr	%r2,%r3
+	br	%r14
+3:	mvc	0(256,%r4),0(%r2)
+	la	%r2,256(%r2)
+	la	%r4,256(%r4)
+4:	aghi	%r3,-256
 	jnm	3b
-4:	lgr	%r2,%r3
+5:	ex	%r3,4(%r1)
 	sacf	0
-	br	%r14
+6:	slgr	%r2,%r2
+	br	14
         .section __ex_table,"a"
-	.quad	0b,3b
-	.quad	2b,3b
-	.quad	3b,4b
+	.quad	1b,2b
+	.quad	3b,0b
+	.quad	5b,0b
         .previous
 
         .align 4